This invention relates to pharmaceutically useful compounds, in particular compounds that bind to opiate receptors (e.g. mu, kappa and delta opioid receptors).
Compounds that bind to such receptors are likely to be useful in the treatment of diseases mediated by opiate receptors, for example irritable bowel syndrome; constipation; nausea; vomiting; and pruritic dermatoses, such as allergic dermatitis and atopy in animals and humans. Compounds that bind to opiate receptors have also been indicated in the treatment of eating disorders, opiate overdoses, depression, smoking and alcohol addiction, sexual dysfunction, shock, stroke, spinal damage and head trauma.
There is a particular need for an improved treatment of itching. Itching, or pruritus, is a common dermatological symptom that can give rise to considerable distress in both humans and animals. Pruritus is often associated with inflammatory skin diseases which may be caused by hypersensitivity reactions, including reactions to insect bites, such as flea bites, and to environmental allergens, such as house dust mite or pollen; by bacterial and fungal infections of the skin; or by ectoparasite infections.
Existing treatments that have been employed in the treatment of pruritus include the use of corticosteroids and antihistamines. However, both of these treatments are known to have undesirable side effects. Other therapies that have been employed include the use of essential fatty acid dietary supplements, though these have the disadvantages of being slow to act, and of offering only limited efficacy against allergic dermatitis. A variety of emollients such as soft paraffin, glycerine and lanolin are also employed, but with limited success.
Thus, there is a continuing need for alternative and/or improved treatments of pruritus.
Certain 4-arylpiperidine-based compounds are disclosed in inter alia European patent applications EP 287339, EP 506468, EP 506478 and J. Med. Chem. 1993, 36, 2833-2850 as opioid antagonists. In addition, International Patent Application WO 95/15327 discloses azabicycloalkane derivatives useful as neuroleptic agents.
According to the invention there is provided compounds of formula I: 
wherein Het1 represents a 5- or 6-membered heterocyclic ring comprising at least one atom selected from nitrogen, oxygen and sulfur, which ring is optionally fused to a 5- or 6-membered ring, which latter ring optionally contains one or more heteroatoms selected from nitrogen, oxygen and/or sulfur, and which heterocyclic ring system (Het1) is optionally substituted by one or more substituents selected from halo, nitro, xe2x80x94OH, xe2x95x90O, Si(R4a)(R4b)(R4c), N(R5a)(R5b), SR6a, N(R6b)S(O)2R7a, N(R6c)C(O)OR7b, N(R6d)C(O)R7c, C1-C6 alkyl, C1-C6 alkoxy or C3-C6 cycloalkyl (which latter three groups are optionally substituted by one or more halo atoms); R4a to R4c independently represent C1-C6 alkyl or aryl;
R5a and R5b independently represent H, C1-C6 alkyl, C1-C4 alkylphenyl, aryl (which latter three groups are optionally substituted by one or more substituents selected from OH, nitro, amino, halo, C1-C4 alkyl or C1-C4 alkoxy (which latter two groups are optionally substituted by one or more halo atoms)) or, together with the N-atom to which they are attached, form a 4- to 6-membered heterocyclic ring (which ring is optionally substituted by one or more substituents selected from C1-C4 alkyl, C1-C4 alkoxy, OH, xe2x95x90O, nitro, amino or halo);
R6a to R6d each independently represent H, C1-C6 alkyl, C1-C4 alkylphenyl or aryl (which latter three groups are optionally substituted by one or more substituents selected from OH, nitro, amino, halo, C1-C4 alkyl or C1-C4 alkoxy (which latter two groups are optionally substituted by one or more halo atoms));
R7a to R7c independently represent C1-C6 alkyl, C1-C4 alkylphenyl or aryl, which four groups are all optionally substituted by one or more substituents selected from OH, nitro, amino, halo, C1-C4 alkyl or C1-C4 alkoxy (which latter two groups are optionally substituted by one or more halo atoms);
R1 and R2 are each independently H or C1-C4 alkyl;
R3 represents aryl (optionally substituted by one or more substituents selected from OH, nitro, halo, CN, CH2CN, CONH2, C1-C4 alkyl, C1-C4 alkoxy, C1-C5 alkanoyl (which latter three groups are optionally substituted by one or more halo atoms) and xe2x80x94N(R8a)(R8b)), C1-C10 alkyl, C3-C10 alkenyl or C3-C10 alkynyl wherein said alkyl, alkenyl or alkynyl groups are optionally substituted and/or terminated by one or more substituents selected from OR8c, S(O)pR8d, CN, halo, C2-C6 alkanoyl, C1-C6 alkoxy carbonyl, C2-C6 alkanoyloxy, C3-C8 cycloalkyl, C4-C9 cycloalkanoyl, N(R9a)S(O)2R10, Het2, aryl, adamantyl (which latter two groups are optionally substituted by one or more substituents selected from OH, nitro, amino, halo, CN, CH2CN, CONH2, C1-C4 alkyl, C1-C4 alkoxy and C1-C5 alkanoyl (which latter three groups are optionally substituted by one or more halo atoms)), or xe2x80x94Wxe2x80x94A1xe2x80x94N(R9b)(R9c);
p is 0, 1 or 2;
W represents a single bond, C(O) or S(O)q;
A1 represents a single bond or C1-C10 alkylene;
provided that when both W and A1 represent single bonds, then the group xe2x80x94N(R9b)(R9c) is not directly attached to an unsaturated carbon atom;
q is 0, 1 or 2;
R8a to R8d each independently represent H, C1-C10 alkyl, C3-C10 alkenyl, C3-C10 alkynyl, C3-C8 cycloalkyl, C1-C4 alkylphenyl, aryl (which latter six groups are optionally substituted by or one or more substituents selected from OH, nitro, amino, halo, CN, CH2CN, CONH2, C1-C4 alkyl, C1-C4 alkoxy and C1-C5 alkanoyl (which latter three groups are optionally substituted by one or more halo atoms)) or Het3;
provided that R8d does not represent H when p represents 1 or 2;
R9a to R9c each independently represent H, C1-C10 alkyl, C3-C10 alkenyl, C3-C10 alkynyl, C3-C8 cycloalkyl, C1-C4 alkylphenyl, aryl (which latter six groups are optionally substituted by or one or more substituents selected from OH, nitro, amino, halo, CN, CH2CN, CONH2, C1-C4 alkyl, C1-C4 alkoxy and C1-C5 alkanoyl (which latter three groups are optionally substituted by one or more halo atoms)), Het4, or R9b and R9c together represent unbranched C2-C6 alkylene which alkylene group is optionally interrupted by O, S and/or an N(R11) group and is optionally substituted by one or more C1-C4 alkyl groups;
R10 represents C1-C6 alkyl, C3-C8 cycloalkyl, C1-C4 alkylphenyl or aryl, which four groups are optionally substituted by or one or more substituents selected from C1-C4 alkyl, C1-C4 alkoxy, OH, nitro, amino or halo;
R11 represents H, C1-C6 alkyl, C3-C8 cycloalkyl, A2xe2x80x94(C3-C8 cycloalkyl) or
A2-aryl;
A2 represents C1-C6 alkylene;
Het2, Het3 and Het4 independently represent 3-to 8-membered heterocyclic groups, which groups contain at least one heteroatom selected from oxygen, sulfur and/or nitrogen, which groups are optionally fused to a benzene ring, and which groups are optionally substituted in the heterocyclic and/or fused benzene ring part by one or more substituents selected from OH, xe2x95x90O, nitro, amino, halo, CN, aryl, C1-C4 alkyl, C1-C4 alkoxy and C1-C5 alkanoyl (which latter three groups are optionally substituted by one or more halo atoms);
X is H, halo, C1-C4 alkyl or C1-C4 alkoxy (which latter two groups are optionally substituted by one or more halo atoms);
n is 0, 1 or 2;
or pharmaceutically, or veterinarily, acceptable derivatives thereof;
which compounds are referred to together hereinafter as xe2x80x9cthe compounds of the invention.xe2x80x9d
In the definitions used herein, alkyl, alkylene, alkoxy, alkoxy carbonyl, alkanoyl, alkanoyloxy, alkenyl, alkynyl and the alkyl parts of alkylphenyl and aryl alkoxy groups may, when there is a sufficient number of carbon atoms, be straight or branched-chain and/or optionally interrupted by one or more oxygen and/or sulfur atom(s). The term halo includes fluoro, chloro, bromo or iodo. The term xe2x80x9carylxe2x80x9d includes optionally substituted phenyl, naphthyl and the like, and xe2x80x9caryloxyxe2x80x9d includes optionally substituted phenoxy and naphthyloxy and the like. Unless otherwise specified, aryl and aryloxy groups are optionally substituted by one or more (e.g. one to three) substituents selected from OH, nitro, amino, halo, CN, CH2CN, CONH2, C1-C4 alkyl, C1-C4 alkoxy C1-C4 alkoxy carbonyl and C1-C5 alkanoyl (which latter four groups are optionally substituted by one or more halo atoms).
The heterocyclic rings that Het1, Het2, Het3 and Het4 represent may be fully saturated, partially unsaturated and/or wholly or partially aromatic in character. Specific rings that may be mentioned include: for Het1, adenine, benzimidazole, benzoxadiazole, benzoxazole, benzthiazole, cinnoline, cytosine, furan, furoxan, guanine, hydroxypyridine, hypoxanthine, imidazole, 1H-imidazo[4,5-b]pyrazine, indole, isoquinoline, isothiazole, isoxazole, 1,2,4-oxadiazole, 1,2,5-oxadiazole, 1,3,4-oxadiazole, oxazole, phthalazine, purine, pyrazine, pyrazole, pyridazine, pyridine, pyridine N-oxide, pyrimidine, pyrrole, quinazoline, quinoline, quinoxaline, 4,5,6,7-tetrahydrobenzimidazole, 4,5,6,7-tetrahydrobenzoxazole, 4,5,6,7-tetrahydro-1H-imidazo[4,5-b]-pyrazine, 1,2,4,5-tetrazine, tetrazole, 1,2,3-thiadiazole, 1,2,4-thiadiazole, 1,2,5-thiadiazole, 1,3,4-thiadiazole, thiazole, thiophene, thymine, 1,2,3-triazine, 1,2,4-triazine, 1,3,5-triazine, 1,2,3-triazole, 1,2,4-triazole and uracil; for Het2, dioxane, dioxolane, morpholine, piperidine, perhydroazepine, tetrahydrofuran, tetrahydropyran or tetrazole. Substituents on Het1, Het2, Het3, and Het4 groups may be located at any point on the ring/fused ring system.
For the avoidance of doubt, when Het (Het1, Het2, Het3 and Het4) groups are at least part-saturated, possible points of substitution include the atom (e.g. the carbon atom) at the point of attachment of the Het group to the rest of the molecule. Het2, Het3 and Het4 groups may also be attached to the rest of the molecule via a heteroatom.
The piperidine moiety in compounds of formula I may be in N-oxidised form. Sulfur atoms that may interrupt (e.g. alkyl) substituents in compounds of formula I may be present in oxidised form (e.g. as sulfoxides or sulfones). All Het1, Het2, Het3 and Het4 groups may also be in N- or S-oxidized forms.
The term xe2x80x9cpharmaceutically, or veterinarily, acceptable derivativesxe2x80x9d includes non-toxic salts. Salts which may be mentioned include: acid addition salts, for example, salts formed with sulfuric, hydrochloric, hydrobromic, phosphoric, hydroiodic, sulfamic, organo-sulfonic, citric, carboxylic (e.g. acetic, benzoic, etc.), maleic, malic, succinic, tartaric, cinnamic, ascorbic and related acids; base addition salts; salts formed with bases, for example, the sodium, potassium and C1-C4 alkyl ammonium salts.
The compounds of the invention may also be in the form of quaternary ammonium salts, e.g. at the piperidine moiety, which salts may be formed by reaction with a variety of alkylating agents, such as an alkyl halide or an ester of sulfuric, or an aromatic sulfonic, acid.
The compounds of the invention may exhibit tautomerism. All tautomeric forms of the compounds of formula I are included within the scope of the invention.
The compounds of the invention contain one or more asymmetric centres and thus they can exist as enantiomers and diastereomers. Diastereoisomers may be separated using conventional techniques e.g. by fractional crystallisation or chromatography. The various stereoisomers may be isolated by separation of a racemic or other mixture of the compounds using conventional techniques e.g. fractional crystallisation or HPLC. The desired optical isomers may be prepared by reaction of the appropriate optically active starting materials under conditions which will not cause racemisation or epimerisation. Alternatively, the desired optical isomers may be prepared by resolution, either by HPLC of the racemate using a suitable chiral support or, where appropriate, by fractional crystallisation of the diastereoisomeric salts formed by reaction of the racemate with a suitable optically active acid or base. The invention includes the use of both the separated individual isomers as well as mixtures of isomers.
Also included within the scope of the invention are radio-labelled derivatives of compounds of formula I which are suitable for biological studies.
Preferred compounds of the invention include those wherein:
Het1 is attached in the meta- position relative to the piperidine ring;
R1 represents C1-C2 alkyl;
R2 represents H or C1-C2 alkyl;
R3 represents saturated C1-C10 (e.g. C1-C8) alkyl, optionally interrupted by oxygen and/or optionally substituted and/or terminated by one or more substituents selected from CN, halo, C1-C6 alkoxy carbonyl, C2-C6 alkanoyl, C2-C6 alkanoyloxy, C3-C8 cycloalkyl, C4-C9 cycloalkanoyl, OR8c, N(R9a)S(O)2R10, Het2, phenyl (which latter group is optionally substituted by one or more substituents selected from OH, C1-C4 alkyl, C1-C4 alkoxy, C2-C5 alkanoyl, halo, nitro, amino, CN, CH2CN, CONH2 and CF3), and/or xe2x80x94Wxe2x80x94A1xe2x80x94N(R9b)(R9c);
R8c represents H, C1-C6 alkyl, C3-C8 cycloalkyl, C1-C4 alkylphenyl or phenyl (which latter two groups are optionally substituted by one or more substituents selected from OH, C1-C4 alkyl, C1-C4 alkoxy, C2-C5 alkanoyl, halo, nitro, amino, CN, CH2CN, CONH2 and CF3);
R9a to R9c each independently represent H, C1-C4 alkyl, C1-C2 alkylphenyl or phenyl (which latter two groups are optionally substituted by or one or more substituents selected from C1-C2 alkyl, C1-C2 alkoxy, OH or halo);
R10 represents C1-C4 alkyl or aryl, which two groups are optionally substituted by or one or more substituents selected from C1-C2 alkyl, C1-C2 alkoxy, nitro or halo;
W represents C(O) or S(O)2;
A1 represents a single bond or C1-C4 alkylene.
More preferred compounds of the invention include those wherein:
Het1 represents one of the rings specifically identified hereinbefore in respect of Het1;
R1 represents methyl;
R2 represents H or methyl;
R3 represents linear, saturated C1-C7 alkyl, optionally substituted by one or more substituents selected from CN, halo, C1-C2 alkoxy carbonyl, OR8c, N(H)S(O)2R10, Het2, phenyl (which latter group is optionally substituted by one or more substituents selected from C1-C2 alkyl, C1-C2 alkoxy and halo), or C(O)N(R9b)(R9c);
R8c represents H, C1-C4 alkyl, phenyl or C1-C2 alkylphenyl (which latter three groups are optionally substituted by one or more substituents selected from C1-C2 alkyl, C1-C2 alkoxy and halo);
R9b and R9c independently represent H, C1-C4 alkyl or C1-C2 alkylphenyl;
R10 represents C1-C2 alkyl;
X represents halo, particularly fluoro;
n represents 1 or, preferably, 0.
Still further preferred compounds of the invention include those wherein:
Het1 represents a 5- or 6-membered heterocyclic ring comprising at least one nitrogen and/or at least one oxygen atom, which ring is optionally substituted by one or more substituents selected from Si(R4a)(R4b)(R4c), halo, thiobenzyl or C1-C6 alkyl;
R1and R2 both represent methyl groups in the mutually trans configuration;
R3 represents benzyl, 2-(benzyloxy)ethyl, N-benzyl-3-propanamido, 2-butoxyethyl, n-butyl, N,N-diethyl-3-propanamido, 3-(2,5-dimethoxy-phenoxy)propyl, 2-(1,3-dioxan-2-yl)ethyl, 4-(1,3-dioxolan-2-yl)butyl, 2-(1,3-dioxolan-2-yl)ethyl, 2-ethanesulfonamidoethyl, 1-ethoxycarbonyl-methyl, 3-ethoxypropyl, 2-(4-fluorophenyl)ethyl, 6-hexanenitrile, n-hexyl, 3-hydroxy-3-phenylpropyl, 4-methoxybutyl, 5-methoxycarbonylpentyl, 2-(2-methoxyethoxy)ethyl, 2-(3-methylphenyl)ethyl, 3-(4-morpholino)-propyl, 5-pentanenitrile, n-pentyl, 2-(1-perhydroazepinyl)ethyl, 2-phenoxyethyl, 3-phenoxypropyl, 2-phenylethyl, 3-phenylpropyl, 2-(1-piperidino)ethyl, 3-(1-piperidino)propyl, N-propyl-3-propanamido, 2-propoxyethyl, 3-tetrahydro-3-furanylpropyl, 3-tetrahydro-2H-pyran-2-ylpropyl or 3-(tetrazol-1-yl)-propyl;
R4a to R4c independently represent C1-C6 alkyl.
Particularly preferred compounds of the invention include those wherein:
Het1 represents preferably unsubstituted 2- or 4-imidazole, tetrazole, 5-oxazole, 5-isoxazole, 4- or 5-pyrazole, 1,2,3- or 1,2,4-triazole.
Preferred compounds of the invention include the compounds of the Examples described hereinafter.
According to a further aspect of the invention there is provided processes for the preparation of compounds of the invention, as illustrated below.
The following processes are illustrative of the general synthetic procedures which may be adopted in order to obtain the compounds of the invention.
1. Compounds of formula I may be prepared by transition-metal- (for example, palladium-) catalysed cross-coupling between a compound of formula II, 
wherein L is a suitable leaving group such as halogen, preferably bromine or iodine, or a sulfonate such as trifluoromethanesulfonate, and R1, R2, R3, X and n are as hereinbefore defined, with a compound of formula III,
Het1xe2x80x94Mxe2x80x83xe2x80x83III
where M is a tin-containing moiety (e.g. tributylstannyl), a boron derivative (e.g. a boronic acid), or a zinc halide (which may be formed in situ from the corresponding halide) and Het1 is as hereinbefore defined, for example at between room temperature and boiling point in a reaction-inert solvent (e.g. dimethylformamide) in the presence of an appropriate coupling agent (e.g. palladium(II) chloride, tris(dibenzylideneacetone)-dipalladium(0) combined with triphenylarsine, or tetrakis(triphenyl-phosphine)palladium(0)).
2. Compounds of formula I in which Het1 represents 1H-1,2,3-triazol-4-yl, optionally substituted by Si(R4a)(R4b)(R4c), C1-C6 alkyl or C1-C6 haloalkyl, wherein R4a to R4c are as hereinbefore defined, may be prepared by reaction of a nitrile of formula IV, 
wherein R1, R2, R3, X and n are as hereinbefore defined, with a compound of formula V,
R12CHN2xe2x80x83xe2x80x83V
wherein R12 represents H, Si(R4a)(R4b)(R4c) or C1-C6 alkyl, which latter group is optionally substituted by one or more halo atoms, and R4a to R4c are as hereinbefore defined, for example at between xe2x88x9210xc2x0 C. and room temperature in the presence of a suitable strong base (e.g. n-butyllithium) and a reaction-inert organic solvent (tetrahydrofuran).
Compounds of formula IV may be prepared by reaction of a compound of formula VI, 
wherein R1, R2, R3, X and n are as hereinbefore defined with an alkali metal cyanide (e.g. potassium cyanide), for example at raised temperature in the presence of a reaction-inert solvent (e.g. N-methylpyrrolidine) and a suitable catalyst (e.g. palladium(II) acetate combined with 1,1xe2x80x2-bis(diphenylphosphino)ferrocene).
Compounds of formula VI may be prepared by reaction of a corresponding compound of formula VII, 
wherein R1, R2, R3, X and n are as hereinbefore defined, with an appropriate triflating agent (e.g. N-phenyltrifluoromethanesulfonimide), for example at between 0xc2x0 C. and room temperature in the presence of a reaction-inert organic solvent (e.g. dichloromethane) and a suitable base (e.g. triethylamine).
Compounds of formula VII may be prepared by reaction of a corresponding compound of formula VIII, 
with a compound of formula IX,
R3L1xe2x80x83xe2x80x83IX
wherein R3 is as hereinbefore defined, and L1 represents a leaving group (e.g. halo, alkanesulfonate, perfluoroalkanesulfonate or arenesulfonate), under conditions that are known to those skilled in the art, which include, for example, alkylation at between room temperature and reflux temperature in the presence of a reaction-inert organic solvent (e.g. N,N-dimethylformamide) and a suitable base (e.g. NaHCO3), and arylation at between room temperature and reflux temperature in the presence of a suitable catalyst system (e.g. tris(dibenzylideneacetone)palladium(0) combined with tri-o-tolylphosphine), an appropriate strong base (e.g. sodium tert-butoxide) and a reaction-inert solvent (e.g. toluene).
3. Compounds of formula I in which Het1 represents 1H-1,2,4-triazol-4-yl, optionally substituted by an R12 group, wherein R12 is as hereinbefore defined, may be prepared by reaction of an imidate of formula X, 
wherein R13 represents C1-C6 alkyl, and R1, R2, R3, X and n are as hereinbefore defined, with a compound of formula XI,
H2NNHCOR12xe2x80x83xe2x80x83XI
wherein R12 is as hereinbefore defined, for example at between room temperature and reflux temperature in the presence of a suitable organic solvent (e.g. an alcohol), followed by, if necessary, continued heating of the reaction until completion in the absence of solvent.
Compounds of formula X may be prepared by methods well known to those skilled in the art. For example, compounds of formula X may be prepared by saturating a solution of a corresponding nitrile of formula IV, as hereinbefore defined, in an alcohol of formula R13OH, wherein R13 is as hereinbefore defined, with gaseous HCl, for example at 0 to 50xc2x0 C.
4. Compounds of formula I in which Het1 represents 1H-1,3-imidazol-2-yl, optionally substituted by up to two R12 groups, wherein R12 is as hereinbefore defined, may be prepared by reaction of a corresponding compound of formula X, as hereinbefore defined, with a compound of formula XII,
H2NCH(R12b)C(OMe)2R12axe2x80x83xe2x80x83XII
wherein independent substituents R12a and R12b represent R12, and R12 is as hereinbefore defined, for example at between room temperature and reflux temperature in the presence of a suitable organic solvent (e.g. an alcohol), followed by, if necessary, continued heating of the reaction until completion in the absence of solvent.
5. Compounds of formula I in which Het1 represents 1H-benzimidazol-2-yl, 1H-benzoxazol-2-yl, 1H-benzthiazol-2-yl (all of which are optionally substituted in the benzene ring part) may be prepared by reaction of a corresponding compound of formula X, as hereinbefore defined, with a compound of formula XIII, 
wherein D represents one to four substituents as defined hereinbefore in respect of Het1 and E represents O, S or NH, under conditions known to those skilled in the art, for example at between room temperature and reflux temperature in the presence of a suitable organic solvent (e.g. an alcohol), followed by, if necessary, continued heating of the reaction until completion in the absence of solvent.
6. Compounds of formula I in which Het1 represents 5-chloro-1,2,4-thiadiazol-3-yl may be prepared by reaction of a corresponding compound of formula XIV, 
or a suitable (e.g. hydrogen halide) adduct thereof, wherein R1, R2, R3, X and n are as hereinbefore defined, with trichloromethanesulfenyl chloride, for example at between xe2x88x9210 and +10xc2x0 C. in the presence of a reaction-inert solvent (e.g. dichloromethane) and optionally in the presence of a suitable base (e.g. aqueous sodium hydroxide).
Compounds of formula XIV may be prepared by reaction of a compound of formula IV, as hereinbefore defined, with ammonia and/or or a suitable adduct thereof (e.g. a hydrohalide), for example at between room temperature and 100xc2x0 C., optionally at elevated pressure and optionally in the presence of a suitable solvent (e.g. water, a lower alkyl alcohol such as methanol or ethanol, or an appropriate mixture thereof).
7. Compounds of formula I in which Het1 represents 1H-1,3-imidazol-4-yl may be prepared by desulfurisation of a corresponding compound of formula I in which Het1 represents 2-thiobenzylated 1H-1,3-imidazol-4-yl, for example using Raney(copyright) nickel in the presence of a suitable organic solvent (e.g. ethanol) and an appropriate base (e.g. sodium hydroxide).
8. Compounds of formula I in which Het1 represents 2-thiobenzylated 1H-1,3-imidazol-4-yl may be prepared by reaction of a corresponding xcex1-halocarbonyl compound of formula XV, 
wherein R1, R2, R3, X and n are as hereinbefore defined with 2-benzyl-2-thiopseudourea, for example at between room temperature and reflux temperature in the presence of a reaction-inert organic solvent (e.g. N,N-dimethylformamide) and a suitable base (e.g. potassium carbonate).
Compounds of formula XV may be prepared by reaction of a corresponding methylketone of formula XVI, 
wherein R1, R2, R3, X and n are as hereinbefore defined, with trimethylsilylchloride, for example at between xe2x88x9278 and xe2x88x9210xc2x0 C. in the presence of a strong base (e.g. lithium bis(trimethylsilyl)amide) and a reaction-inert organic solvent (e.g. tetrahydrofuran), followed by reaction with bromine.
Compounds of formula XVI may be prepared by reaction of a corresponding triflate of formula VI, as hereinbefore defined, with a compound that provides a suitable source of an acyl anion equivalent (e.g. vinyl butyl ether), for example at between room temperature and reflux temperature in the presence of an appropriate catalyst (e.g. palladium(II) acetate combined with 1,1xe2x80x2-bis(diphenylphosphino)ferrocene), an organic base (e.g. triethylamine) and a suitable solvent (e.g. N,N-dimethyl-formamide), followed by hydrolysis of the resulting enol ether under conditions known to those skilled in the art (for example, by reaction at room temperature with aqueous hydrochloric acid).
Alternatively, compounds of formula XVI may be prepared by reaction of a compound corresponding to a nitrile of formula IV with a methyl-delivering organometallic compound (e.g. methyl lithium), for example at between xe2x88x9280 and 10xc2x0 C. in the presence of a reaction-inert organic solvent (e.g. tetrahydrofuran).
9. Compounds of formula I in which Het1 represents 1H-tetrazol-5-yl may be prepared by reaction of a corresponding compound of formula IV, as hereinbefore defined, with a suitable source of the azide ion (e.g. trimethylsilyl azide), for example at between room temperature and reflux temperature in the presence of a reaction-inert solvent (e.g. toluene) and an appropriate Lewis-acidic catalyst (e.g. dibutyltin oxide).
10. Compounds of formula I wherein R3 represents C1 alkyl optionally substituted by C3-C8 cycloalkyl, Het2, aryl, adamantyl, (which latter two groups are optionally substituted by one or more substituents selected from OH, nitro, amino, halo, CN, CH2CN, CONH2, C1-C4 alkyl, C1-C4 alkoxy and C1-C5 alkanoyl (which latter three groups are optionally substituted by one or more halo atoms)), or R3 represents C2-C10 alkyl, C3-C10 alkenyl or C3-C10 alkynyl (which three groups are all optionally substituted by one or more of the relevant substituents identified hereinbefore in respect to R3), which alkyl, alkenyl or alkynyl groups are attached to the piperidine nitrogen atom via a CH2 group, wherein Het2 is as hereinbefore defined, may be prepared by reduction of a corresponding compound of formula XVII, 
wherein R31 represents H, C3-C8 cycloalkyl, Het2, aryl, adamantyl, (which latter two groups are optionally substituted by one or more substituents selected from OH, nitro, amino, halo, CN, CH2CN, CONH2, C1-C4 alkyl, C1-C4 alkoxy and C1-C5 alkanoyl (which latter three groups are optionally substituted by one or more halo atoms)), C1-C9 alkyl, C2-C9 alkenyl or C2-C9 alkynyl, which alkyl, alkenyl or alkynyl groups are optionally substituted and/or terminated by one or more substituents selected from OR8c, S(O)pR8d, CN, halo, C1-C6 alkoxy carbonyl, C2-C6 alkanoyl, C2-C6 alkanoyloxy, C3-C8 cycloalkyl, C4-C9 cycloalkanoyl, N(R9a)S(O)2R10, Het2, aryl, adamantyl (which latter two groups are optionally substituted by one or more substituents selected from OH, nitro, amino, halo, CN, CH2CN, CONH2, C1-C4 alkyl, C1-C4 alkoxy and C1-C5 alkanoyl (which latter three groups are optionally substituted by one or more halo atoms)), or xe2x80x94Wxe2x80x94A1xe2x80x94N(R9b)(R9c), and R1, R2, R8c, R8d, R9a to R9c, R10, Het1, Het2, n, p, W, X and A1 are as hereinbefore defined, using a suitable reducing agent (e.g. lithium aluminium hydride or a borane derivative), for example as described hereinbefore.
Compounds of formula XVII may be prepared by reaction of a corresponding compound of formula XVIII, 
wherein Het1, R1, R2, X and n are as hereinbefore defined with a compound of formula XIX,
R31CO2xe2x80x83xe2x80x83H XIX
or a suitable (e.g. carboxylic acid) derivative thereof (e.g. an acid halide or anhydride), wherein R31 is as hereinbefore defined, using coupling conditions known to those skilled in the art.
Compounds of formulae XVII and XVIII may be prepared from appropriate precursors by analogy with methods disclosed herein that describe to the introduction, or formation, of a Het1 group.
11. Compounds of formula I in which Het1 represents 1H-pyrazol-3-yl may be prepared by reaction of a corresponding xcex1,xcex2-unsaturated ketone of formula XX, 
wherein R1, R2, R3, X and n are as hereinbefore defined, with hydrazine, for example at between room temperature and reflux temperature in the presence of a reaction-inert solvent (e.g. a methanol/water mixture).
Compounds of formula XX may be prepared by aldol condensation of a corresponding methyl ketone of formula XVI, as hereinbefore defined, with dimethylaminoacetaldehyde dimethylacetal, for example at between room temperature and reflux temperature in the presence of a reaction-inert organic solvent (e.g. N,N-dimethylformamide).
12. Compounds of formula I wherein Het1 represents 1H-pyrazol-4-yl may be prepared by reaction of a corresponding compound of formula VI, as hereinbefore defined, with a compound of formula XXI, 
for example at between room temperature and reflux temperature in the presence of a reaction-inert solvent (e.g. N,N-dimethylformamide), an appropriate coupling agent (e.g. tris(dibenzylideneacetone)dipalladium(0) combined with triphenylarsine) and a suitable source of a halide ion (e.g. lithium chloride).
13. Compounds of formula I wherein Het1 represents oxazol-5-yl, thiazol-5-yl or imidazol-5-yl (which three groups are all optionally substituted in the 4-position by R12, wherein R12 is as hereinbefore defined, and which imidazol-5-yl group is substituted at the 1-position by C1-C6 alkyl, C1-C6 alkoxy or C3-C6 cycloalkyl (which latter three groups are optionally substituted by one or more halo atoms)) may be prepared by reaction of a corresponding compound of formula XXII, 
wherein G represents NR14, O or S, R14 represents C1-C6 alkyl, C1-C6 alkoxy or C3-C6 cycloalkyl (which latter three groups are optionally substituted by one or more halo atoms), and R1, R2, R3, X and n are as hereinbefore defined, with a compound of formula XXIII,
CNCH(R12)L2xe2x80x83xe2x80x83XXIII
wherein L2 represents a group capable, when attached to a C2 alkylene unit, of undergoing 1,2-elimination (relative to the L2 group, e.g. an alkyl or aryl sulfoxide or sulfone), and R12 is as hereinbefore defined, for example at between room and reflux temperature in the presence of an appropriate base (e.g. potassium carbonate) and a reaction-inert solvent (e.g. a lower alkyl alcohol, such as methanol).
Compounds of formula XXII in which G represents O may be prepared from a corresponding vinyl derivative of formula XXIV, 
wherein R1, R2, R3, X and n are as hereinbefore defined, by reaction with a suitable dihydroxylating reagent (e.g. sub-stoichiometric OSO4 combined with morpholine N-oxide), for example at between 0xc2x0 C. and refluxtemperature in the presence of a reaction-inert solvent (e.g. a water/acetone mixture) and an appropriate reagent to effect 1,2-diol oxidative cleavage (e.g. sodium periodate).
Compounds of formula XXII in which G represents NR14, wherein R14 is as hereinbefore defined, may be prepared by reaction of a corresponding compound in which G represents 0 with a compound of formula XXV,
R14xe2x80x94NH2xe2x80x83xe2x80x83XXV
wherein R14 is as hereinbefore defined, for example at between room and reflux temperature in the presence of a reaction-inert solvent (e.g. a lower alkyl alcohol such as methanol or ethanol), and optionally in the presence of a suitable Lewis-acidic catalyst.
Compounds of formula XXII in which G represents S may be prepared by reaction of a corresponding compound in which G represents O with a reagent that effects oxygen-sulfur exchange (e.g. Lawesson""s Reagent), for example at between room and reflux temperature in the presence of a reaction-inert solvent (e.g. toluene).
Compounds of formula XXIV can be prepared from a corresponding compound of formula VI, as hereinbefore defined, by reaction with a suitable source of vinyl anion equivalent (e.g. vinyltributyltin), for example at between room temperature and reflux temperature in the presence of a reaction-inert solvent (e.g. THF), an appropriate coupling agent (e.g. tetrakis(triphenylphosphine)palladium(0)) and a suitable source of halide ion (e.g. lithium chloride).
14. Compounds of formula I wherein Het1 represents isoxazol-5-yl may be prepared by reaction of a corresponding compound of formula XX, as hereinbefore defined, with a suitable form of hydroxylamine, for example at between room temperature and reflux temperature in the presence of a reaction-inert solvent (e.g. a methanol/water mixture).
15. Compounds of formula I in which Het1 represents 1H-1,2,3-triazol-4-yl, optionally substituted by Si(R4a)(R4b)(R4c), C1-C6 alkyl or C1-C6 haloalkyl or halo, wherein R4a to R4c are as hereinbefore defined, may alternatively be prepared by reaction of a corresponding compound of formula XXVI, 
wherein R15 represents H, Si(R4a)(R4b)(R4c), halo or C1-C6 alkyl, which latter group is optionally substituted by one or more halo atoms, and R1, R2, R3, R4a to R4c, L2, X and n are as hereinbefore defined, with a suitable source of the azide ion (e.g. sodium azide), for example at between room and reflux temperature in the presence of a reaction-inert solvent (e.g. N,N-dimethylformamide).
Compounds of formula XXVI may be prepared by reaction of a compound of formula XXII, as hereinbefore defined, in which G represents O, with a compound of formula XXVII,
L2xe2x80x94CH2xe2x80x94R15xe2x80x83xe2x80x83XXVII
wherein L2 and R15 are as hereinbefore defined, for example at between xe2x88x9280xc2x0 C. and room temperature in the presence of a strong base (e.g. n-butyl lithium) and a reaction-inert solvent (e.g. THF), followed by dehydration of the resultant hydroxy compound under conditions well known to those skilled in the art (e.g. by reaction with methanesulfonyl chloride in the presence of triethylamine).
16. Compounds of formula I may be prepared by reaction of a corresponding compound of formula XVIII, as hereinbefore defined, with a compound of formula IX, as hereinbefore defined, under conditions that are well known to those skilled in the art, for example as described hereinbefore in respect of the production of compounds of formula VII.
17. Compounds of formula I wherein R3 represents C1 alkyl, which, in place of being optionally substituted by the substituents as defined hereinbefore, is instead optionally substituted by R31, wherein R31 is as hereinbefore defined, may be prepared by reaction of a corresponding compound of formula XVIII, as hereinbefore defined, with a compound of formula XXVIII,
R31CHOxe2x80x83xe2x80x83XXVIII
wherein R31 is as hereinbefore defined, for example in the presence of a suitable reducing agent (e.g. sodium borohydride, sodium cyano-borohydride or sodium triacetoxyborohydride) and an appropriate solvent (e.g. methanol).
18. Compounds of formula I wherein R3 is a C1-C10 alkyl, C4-C10 alkenyl or C4-C10 alkynyl group that is fully saturated from 1- to 3-C (relative to the piperidine N-atom), and which R3 group is substituted at 2-C (relative to the piperidine N-atom) by S(O)R8d, S(O)2R8d, alkanoyl, cycloalkanoyl, alkoxy carbonyl, CN, xe2x80x94C(O)xe2x80x94A1xe2x80x94N(R9b)(R9c), xe2x80x94S(O)xe2x80x94Alxe2x80x94N(R9b)(R9c), or xe2x80x94S(O)2xe2x80x94A1xe2x80x94N(R9b)(R9c), wherein R8d, R9b, R9c and A1 are as hereinbefore defined, may be prepared by reaction of a corresponding compound of formula XVIII, as hereinbefore defined, with a compound of formula XXIX,
R3axe2x80x94Zxe2x80x83xe2x80x83XXIX
wherein R3a represents R3 as hereinbefore defined except that it does not represent aryl, and that the R3a chain contains an additional carbon-carbon double bond xcex1,xcex2 to the Z-substituent, and Z represents S(O)R8d, S(O)2R8d, alkanoyl, cycloalkanoyl, alkoxy carbonyl, CN, xe2x80x94C(O)xe2x80x94A1xe2x80x94N(R9b)(R9c), xe2x80x94S(O)xe2x80x94A1xe2x80x94N(R9b)(R9c), or xe2x80x94S(O)2xe2x80x94A1xe2x80x94N(R9b)(R9c), wherein R8d, R9b, R9c and A1 are as hereinbefore defined, for example at between room and reflux temperature in the presence of a reaction-inert solvent (e.g. THF).
Compounds of formulae II, III, V, VIII, IX, XI, R13OH, XII, XIII, XIX, XXI, XXIII, XXIV, XXVII, XXVIII, XXIX, and derivatives thereof, when not commercially available or not subsequently described, may be obtained either by analogy with the processes described herein, or by conventional synthetic procedures, in accordance with standard techniques, from readily available starting materials using appropriate reagents and reaction conditions. For example, Het1 or Het1-M groups in compounds of formulae I, III, XVII, XVIII and XXI may also be prepared by, or by analogy with, the methods disclosed in European patent application EP 590 971, Houben-Weyl Methods of Organic Chemistry, Additional and Supplementary Volumes to the 4th Edition (Volumes E6a, E6b, E6b2, E7a, E7b, E8a, E8b, E8c, E8d, E9, E9a), edited by E Schaumann and R Kreher, Thieme (Stuttgart) or Comprehensive Heterocyclic Chemistry II, edited by A R Katritsky, C W Rees and EFV Scriven, 1st Edition, Elsevier Science Ltd., Volumes 1-11 (1996). Conventional synthetic procedures, and standard techniques also include, for example, those relating to process 1 described hereinbefore, examples of which may be found in: xe2x80x9cPalladium Reagents in Organic Synthesisxe2x80x9d RF Heck, Academic Press (1985); xe2x80x9cComprehensive Organometallic Chemistryxe2x80x9d, edited by AG Davies, 2nd Edition, Volume 12, Chapter 3, Section D, Pergamon Press (1995); J K Stille, Angew. Chem. Intl. Ed. Eng., 1986, 25, 508; A Suzuki, N Niyaura, Chem. Rev. 1995, 95, 2457; xe2x80x9cOrganometallics in Synthesis A Manualxe2x80x9d, M. Schlosser, John Wiley and Sons (1994); xe2x80x9cMetal-catalysed Cross-coupling Reactionsxe2x80x9d, F Diedrich and P J Stang, Wiley-Vch (1998); and xe2x80x9cPalladium Reagents and Catalysts Innovations in Organic Synthesisxe2x80x9d, J Tsuji, John Wiley and Sons (1995), the disclosures in which documents are hereby incorporated by reference.
Substituents on alkyl, heterocyclic and aryl groups in the above-mentioned compounds may also be introduced, removed and interconverted, using techniques which are well known to those skilled in the art (including those specifically disclosed hereinbefore). For example, nitro may be reduced to amino, OH may be alkylated to give alkoxy, alkoxy and alkanoyloxy may be hydrolysed to OH, alkenes may be hydrogenated to alkanes, halo may be hydrogenated to H, etc.
In some cases it is possible to introduce further substituents into the compounds of formula I directly. For example, chlorination of the phenyl group of compounds of formula I, may be performed by reaction with a solution of chlorine in acetic acid.
It will be appreciated by those skilled in the art that heterocycles prepared by the processes described hereinbefore may, if desired, be further substituted by, for example, halogen, nitro and xe2x80x94SR, by treatment with electrophilic reagents such as halosuccinimides, nitric acid and sulfenyl halides. It will further be understood that these substituents may be subjected to further transformations, for example reduction of nitro groups and subsequent acylation or alkylation of the resultant amino groups, to provide further examples within the scope of the invention. These methodologies and their applicability will be known and understood by the skilled person.
Thus, the skilled person will appreciate that various standard substituent or functional group interconversions and transformations within certain compounds of formula I will provide other compounds of formula I.
The compounds of the invention may be isolated from their reaction mixtures using conventional techniques.
It will be appreciated by those skilled in the art that, in the course of carrying out the processes described above, the functional groups of intermediate compounds may need to be protected by protecting groups.
Functional groups which it is desirable to protect include oxo, hydroxy, amino and carboxylic acid. Suitable protective groups for oxo include acetals, ketals (e.g. ethylene ketals) and dithianes. Suitable protective groups for hydroxy include trialkylsilyl and diarylalkylsilyl groups (e.g. tert-butyldimethylsilyl, tert-butyldiphenylsilyl or trimethylsilyl) and tetrahydropyranyl. Suitable protective groups for amino include benzyl, tert-butyloxycarbonyl, 9-fluorenylmethoxycarbonyl or benzyloxycarbonyl. Suitable protective groups for carboxylic acid include C1-C6 alkyl or benzyl esters.
The protection and deprotection of functional groups may take place before or after any of the reaction steps described hereinbefore.
Protective groups may be removed in accordance with techniques which are well known to those skilled in the art.
The use of protecting groups is fully described in xe2x80x9cProtective Groups in Organic Chemistryxe2x80x9d, edited by JWF McOmie, Plenum Press (1973), and xe2x80x9cProtective Groups in Organic Synthesisxe2x80x9d, 2nd edition, TW Greene and PGM Wutz, Wiley-Interscience (1991).
Persons skilled in the art will also appreciate that, in order to obtain compounds of formula I in an alternative, and, on some occasions, more convenient, manner, the individual process steps mentioned hereinbefore may be performed in a different order, and/or the individual reactions may be performed at a different stage in the overall route (i.e. substituents may be added to and/or chemical transformations performed upon, different intermediates to those mentioned hereinbefore in conjunction with a particular reaction). This will depend inter alia on factors such as the nature of other functional groups present in a particular substrate, the availability of key intermediates and the protecting group strategy (if any) to be adopted. Clearly, the type of chemistry involved will influence the choice of reagent that is used in the said synthetic steps, the need, and type, of protecting groups that are employed, and the sequence for accomplishing the synthesis. The procedures may be adapted as appropriate to the reactants, reagents and other reaction parameters in a manner that will be evident to the skilled person by reference to standard textbooks and to the examples provided hereinafter.
It will be appreciated by those skilled in the art that certain protected derivatives of compounds of formula I, which may be made prior to a final deprotection stage, may not possess pharmacological activity as such, but may, in certain instances, be administered orally or parenterally and thereafter metabolised in the body to form compounds of the invention which are pharmacologically active. Such derivatives may therefore be described as xe2x80x9cprodrugsxe2x80x9d. Further, certain compounds of formula I may act as prodrugs of other compounds of formula I.
It will be further appreciated by those skilled in the art, that certain moieties, known to those skilled in the art as xe2x80x9cpro-moietiesxe2x80x9d, for example as described in xe2x80x98Design of Prodrugsxe2x80x99 by H. Bundgaard, Elsevier, 1985 (the disclosure in which document is hereby incorporated by reference), may be placed on appropriate functionalities, when such functionalities are present within compounds of formula I.
All protected derivatives, and prodrugs, of compounds of formula I are included within the scope of the invention.
Pharmaceutically acceptable acid addition salts of the compounds of formula I which contain a basic centre may be prepared in a conventional manner. For example, a solution of the free base may be treated with the appropriate acid, either neat or in a suitable solvent, and the resulting salt may then be isolated either by filtration of by evaporation under vacuum of the reaction solvent. Pharmaceutically acceptable base addition salts can be obtained in an analogous manner by treating a solution of a compound of formula I with the appropriate base. Both types of salt may be formed or interconverted using ion-exchange resin techniques.
The above procedures may be adapted as appropriate to the particular reactants and groups involved and other variants will be evident to the skilled chemist by reference to standard textbooks and to the examples provided hereafter to enable all of the compounds of formula I to be prepared.
The compounds of the invention are useful because they possess pharmacological activity in animals, especially mammals including humans. They are therefore indicated as pharmaceuticals and, in particular, for use as animal medicaments.
According to a further aspect of the invention there is provided the compounds of the invention for use as medicaments, such as pharmaceuticals and animal medicaments.
By the term xe2x80x9ctreatmentxe2x80x9d, we include both therapeutic (curative) or prophylactic treatment.
In particular, the compounds of the invention have been found to be useful in the treatment of diseases mediated via opiate receptors, which diseases include irritable bowel syndrome; constipation; nausea; vomiting; pruritus; and conditions characterised by pruritus as a symptom.
Thus, according to a further aspect of the invention there is provided the use of the compounds of the invention in the manufacture of a medicament for the treatment of a disease mediated via an opiate receptor. There is further provided the use of the compounds of the invention in the manufacture of a medicament for the treatment of irritable bowel syndrome; constipation; nausea; vomiting; pruritus or a medical condition characterised by pruritus as a symptom.
The compounds of the invention are thus expected to be useful for the curative or prophylactic treatment of pruritic dermatoses including allergic dermatitis and atopy in animals and humans. Other diseases and conditions which may be mentioned include contact dermatitis, psoriasis, eczema and insect bites.
Thus, the invention provides a method of treating or preventing a disease mediated via an opiate receptor. There is further provided a method of treating irritable bowel syndrome; constipation; nausea; vomiting; pruritus or a medical condition characterised by pruritus as a symptom in an animal (e.g. a mammal), which comprises administering a therapeutically effective amount of a compound of the invention to an animal in need of such treatment.
The compounds of the invention will normally be administered orally or by any parenteral route, in the form of pharmaceutical preparations comprising the active ingredient, optionally in the form of a non-toxic organic, or inorganic, acid, or base, addition salt, in a pharmaceutically acceptable dosage form. Depending upon the disorder and patient to be treated, as well as the route of administration, the compositions may be administered at varying doses (see below).
While it is possible to administer a compound of the invention directly without any formulation, the compounds are preferably employed in the form of a pharmaceutical, or veterinary, formulation comprising a pharmaceutically, or veterinarily, acceptable carrier, diluent or excipient and a compound of the invention. The carrier, diluent or excipient may be selected with due regard to the intended route of administration and standard pharmaceutical, and/or veterinary, practice. Pharmaceutical compositions comprising the compounds of the invention may contain from 0.1 percent by weight to 90.0 percent by weight of the active ingredient.
The methods by which the compounds may be administered for veterinary use include oral administration by capsule, bolus, tablet or drench, topical administration as an ointment, a pour-on, spot-on, dip, spray, mousse, shampoo, collar or powder formulation or, alternatively, they can be administered by injection (e.g. subcutaneously, intramuscularly or intravenously), or as an implant. Such formulations may be prepared in a conventional manner in accordance with standard veterinary practice.
The formulations will vary with regard to the weight of active compound contained therein, depending on the species of animal to be treated, the severity and type of infection and the body weight of the animal. For parenteral, topical and oral administration, typical dose ranges of the active ingredient are 0.01 to 100 mg per kg of body weight of the animal. Preferably the range is 0.1 to 10 mg per kg.
The compositions are preferably formulated in a unit dosage form, each dosage containing from about 1 to about 500 mg, more usually about 5 to about 300 mg, of the active ingredient. The term xe2x80x9cunit dosage formxe2x80x9d refers to physically discreet units suitable as unitary dosages for human subjects and other mammals, each unit containing a predetermined quantity of active material calculated to produce the desired therapeutic effect, in association with a suitable pharmaceutical carrier.
In any event, the veterinary practitioner, or the skilled person, will be able to determine the actual dosage which will be most suitable for an individual patient, which may vary with the species, age, weight and response of the particular patient. The above dosages are exemplary of the average case; there can, of course, be individual instances where higher or lower dosage ranges are merited, and such are within the scope of this invention.
For veterinary use, the compounds of the invention are of particular value for treating pruritus in domestic animals such as cats and dogs and in horses.
As an alternative for treating animals, the compounds may be administered with the animal feedstuff and for this purpose a concentrated feed additive or premix may be prepared for mixing with the normal animal feed.
For human use, the compounds are administered as a pharmaceutical formulation containing the active ingredient together with a pharmaceutically acceptable diluent or carrier. Such compositions include conventional tablet, capsule and ointment preparations which are formulated in accordance with standard pharmaceutical practice.
Compounds of the invention may be administered either alone or in combination with one or more agents used in the treatment or prophylaxis of disease or in the reduction or suppression of symptoms. Examples of such agents (which are provided by way of illustration and should not be construed as limiting) include antiparasitics, e.g. fipronil, lufenuron, imidacloprid, avermectins (e.g. abamectin, ivermectin, doramectin), milbemycins, organophosphates, pyrethroids; antihistamines, e.g. chlorpheniramine, trimeprazine, diphenhydramine, doxylamine; antifungals, e.g. fluconazole, ketoconazole, itraconazole, griseofulvin, amphotericin B; antibacterials, e.g. enroflaxacin, marbofloxacin, ampicillin, amoxycillin; anti-inflammatories e.g. prednisolone, betamethasone, dexamethasone, carprofen, ketoprofen; dietary supplements, e.g. gamma-linoleic acid; and emollients. Therefore, the invention further provides a product containing a compound of the invention and a compound from the above list as a combined preparation for simultaneous, separate or sequential use in the treatment of diseases mediated via opiate receptors.
The skilled person will also appreciate that compounds of the invention may be taken as a single dose on an xe2x80x9cas requiredxe2x80x9d basis (i.e. as needed or desired).
Thus, according to a further aspect of the invention there is provided a pharmaceutical, or veterinary, formulation including a compound of the invention in admixture with a pharmaceutically, or veterinarily, acceptable adjuvant, diluent or carrier.
Compounds of the invention may also have the advantage that, in the treatment of human and/or animal patients, they may be more efficacious than, be less toxic than, have a broader range of activity than, be more potent than, produce fewer side effects than, be more easily absorbed than, or they may have other useful pharmacological properties over, compounds known in the prior art.
The biological activities of the compounds of the present invention were determined by the following test method.
Biological Test
Compounds of the present invention have been found to display activity in binding assays selective for the mu opioid receptor in dog brain. The assays were conducted by the following procedure.
Laboratory bred beagles were used as a source of dog brain tissue. Animals were euthanised, their brains removed and the cerebellum discarded. The remaining brain tissue was sectioned into small pieces approximately 3 g in weight and homogenised in 50 mM Tris pH 7.4 buffer at 4xc2x0 C. using a Kinematica Polytron3 tissue homogeniser. The resulting homogenate was centrifuged at 48,400xc3x97 g for 10 minutes and the supernatant discarded. The pellet was resuspended in Tris buffer and incubated at 37xc2x0 C. for 10 minutes. Centrifugation, resuspension and incubation steps were repeated twice more, and the final pellet was resuspended in Tris buffer and stored at xe2x88x9280xc2x0 C. Membrane material prepared in this manner could be stored for up to four weeks prior to use.
For mu assays, increasing concentrations of experimental compound, (5xc3x9710xe2x88x9212 to 10xe2x88x925 M), Tris buffer and 3H ligand, ([D-Ala2, N-Me-Phe4,Gly-ol5]-Enkephalin, DAMGO), were combined in polystyrene tubes. The reaction was initiated by the addition of tissue, and the mixture was incubated at room temperature for 90 minutes. The reaction was terminated by rapid filtration using a Brandel Cell Harvester3 through Betaplate3 GF/A glass fibre filters pre-soaked in 50 mM Tris pH 7.4, 0.1% polyethylenimine buffer. The filters were then washed three times with 0.5 mL ice-cold Tris pH 7.4 buffer. Washed filters were placed in bags and Starscint3 scintillant added. Bags containing the filters and scintillant were heat sealed and counted by a Betaplate3 1204 beta counter.
Duplicate samples were run for each experimental compound and the data generated was analysed using IC50 analysis software in Graphpad Prism. Ki values were calculated using Graphpad Prism according to the following formula:
Ki=IC50/1+[3H ligand]/KD
where IC50 is the concentration at which 50% of the 3H ligand is displaced by the test compound and KD is the dissociation constant for the 3H ligand at the receptor site.
The invention is illustrated by the following Preparations and Examples in which the following abbreviations may be used:
APCI =atmospheric pressure chemical ionisation
br (in relation to NMR)=broad
DMF=N,N-dimethylformamide
DMSO=dimethylsulfoxide
d (in relation to time)=day
d (in relation to NMR)=doublet
dd (in relation to NMR)=doublet of doublets
dt (in relation to NMR)=doublet of triplets
EtOAc=ethyl acetate
EtOH=ethanol
ESI=electrospray ionisation
h=hour(s)
m (in relation to NMR)=multiplet
MeOH =methanol
min(s)=minute(s)
q (in relation to NMR)=quartet
s (in relation to NMR)=singlet
t (in relation to NMR)=triplet
THF=tetrahydrofuran
When reverse phase HPLC is mentioned in the text the following 2 sets of conditions were employed.
Condition 1: A Phenomenex Magellen3 column, 150xc3x9721 mm, packed with 5xcexc C18 silica, eluting with a gradient of acetonitrile: 0.1 M aqueous ammonium acetate (30:70 to 95:5 over 10 mins, flow rate 20 mL per min).
Condition 2: A Dynamax3 column, 42xc3x97250 mm, packed with 8xcexc C18 silica, eluting with acetonitrile: 0.1 M aqueous ammonium acetate (30:70) at 45 mL per minute.
In both cases, combination and evaporation of appropriate fractions, determined by analytical HPLC, provided the desired compounds as acetate salts.
Analytical HPLC conditions used to highlight appropriate fractions were Phenomenex Magellan3 column, 4.6xc3x97150 mm, packed with 5xcexc C18 silica, eluting with a gradient of acetonitrile: 0.1 M aqueous heptanesulfonic acid (10:90 to 90:10 over 30 min, followed by a further 10 min at 90:10) at 1 mL per minute. Column oven temperature was 40xc2x0 C., and ultraviolet detection of components was made at 220 nM.
When column chromatography is referred to this usually refers to a glass column packed with silica gel (40-63 xcexcm). Pressure of xcx9c165 kPa is generally applied and the ratio of crude product:silica gel required for purification is typically 50:1. Alternatively, an Isolute SPE (solid phase extraction) column or Waters Sep-Pak3 cartridge packed with silica gel may be used under atmospheric pressure. The ratio of crude product to silica gel required for purification is typically 100:1.
The hydrochloride salt may be made by methods commonly known to those skilled in the art of synthetic chemistry. Typically, to a solution of free base in dichloromethane (1 g: 100 mL) was added ethereal hydrochloric acid (1.0 M, 1.2 equivalent), the excess solvent was decanted off and the remaining precipitate was washed three times with ether and then dried in vacuo.
Nuclear magnetic resonance (NMR) spectral data were obtained using a Varian Inova 300 or Varian Inova 400 spectrometer, the observed chemical shifts (xcex4) being consistent with the proposed structures. Mass spectral (MS) data were obtained on a Finnigan Masslab Navigator or a Fisons Instruments Trio 1000 spectrometer. The calculated and observed ions quoted refer to the isotopic composition of lowest mass. HPLC means high performance liquid chromatography. Room temperature means 20 to 25xc2x0 C.